In recent years, demand for high-speed communication in a transmission distance of shorter than or equal to 40 km is abruptly increasing. Enhanced speed of electronic devices such as a semiconductor device that receives and emits optical signals using an optical communication device is receiving attention. An electronic device typified by such a semiconductor device has an optical output of approximately 0.2 to 0.5 mW, and a semiconductor element used as an electronic component has a driving electrical power of approximately 5 mW. However, a semiconductor device having a larger output has an optical output at a level of 1 mW, and a semiconductor element is also required to have a driving electrical power of greater than or equal to 10 mW. Furthermore, a conventional semiconductor device has a transmission speed of approximately 2.5 to 10 Gbps (Giga bit per second), but a semiconductor element that copes with 25 to 40 Gbps has been developed recently. A larger output and enhanced speed have been required for semiconductor devices.
In a semiconductor device that copes with a larger output and enhanced speed, a TO-CAN type package as described in Patent Document 1, for example, is used. The TO-CAN type package connects first portions of signal terminals that are inserted in a through hole of a plate-shaped base body and exposed from a first face of the base body to a semiconductor element mounted on a board mounting portion provided on the first face of the base body. In the TO-CAN type package, the signal terminals have a coaxial line structure and can cope with a larger output and enhanced speed. For the TO-CAN type, the first portions of the signal terminals exposed from the base body do not have the coaxial structure and are not surrounded by an insulating member and a conductive member. Thus, an unnecessary inductance component occurs, and a mismatch of characteristic impedance causes deterioration of electrical characteristics.
In the package disclosed in JP 2015-122466 A, the exposed first portions are covered with the insulating member and a dielectric body is provided between the pair of first portions to prevent deterioration of electrical characteristics. Although the exposed first portions are covered with the insulating member and the dielectric body is provided between the pair of first portions, characteristic impedance abruptly changes at a bonding wire on a tip of each of the first portions. Thus, deterioration of electrical characteristics cannot be sufficiently suppressed in some cases.